Momentary switch with serpentine movable and coil spring stationary contacts

ABSTRACT

An electric switch of the push-button type affording a momentary switching action comprising a spring-biased push-button which in response to the depression thereof causes a cam surface to bear against a springing moving contact member initially to produce bowing of the member so that it makes electrical contact with a fixed contact member in the form of a coil spring and thereafter during the depression of the push-button to permit the compressive forces in the contact member to be released suddenly by snap deflection of the member as it rides over the cam surface thereby to interrupt electrical contact with the member by the straightening of the moving contact member.

United States Patent [191 Beddoe MOMENTARY SWITCH WITH SERPENTINE MOVABLE AND COIL SPRING STATIONARY CONTACTS [75] Inventor: Stanley Beddoe, Fareham, England [73] Assignee: Plessey Handel und Investments A.G., Zug, Switzerland [22] Filed: Jan. 26, 1973 [2]] Appl. No.: 323,012

[30] Foreign Application Priority Data Jan. 19, 1972 Great Britain 2682/72 [52] U.S. Cl 200/160, 200/166 BA [51] Int. Cl. HOIh 13/50 [58] Field of Search 200/166 BA, 160, 159 R [56] References Cited UNITED STATES PATENTS 3,153,130 10/1964 Nenninger 200/160 3,699,296 10/1972 Harris 200/166 BA X FOREIGN PATENTS OR APPLICATIONS 440,419 12/1967 Switzerland 200/160 OTHER PUBLICATIONS lBM Technical Disclosure, Vol. 14, No. 6, p. 1865,

[ 1 May 7,1974

1 1/1971; Wire Contact Data Entry Keyboard Mechanism; by Harris (ll).

Primary Examiner--R0bert K. Schaefer Assistant ExaminerRobert A. Vanderhye Attorney, Agent, or FirmScrivener, Parker, Scrivener & Clarke [5 7] ABSTRACT An electric switch of the push-button type affording a momentary switching action comprising a springbiased push-button which in response to the depression thereof causes a cam surface to bear against a springing moving contact member initially to produce bowing of the member so that it makes electrical contact with a fixed contact member in the form of a coil spring and thereafter during the depression of the push-button to permit the compressive forces in the contact member to be released suddenly by snap deflection of the member as it rides over the cam surface thereby to interrupt electrical contact with the member by the straightening of the moving contact member.

1 Claim, 1 Drawing Figure 1 MOMENTARY SWITCH WITH SERPENTINE MOVABLE AND COIL SPRING STATIONARY CONTACTS This invention relates to electric switches of the push-button type which may be used as key-switches in electronic keyboards.

In many applications of electronic keyboards it is advantageous to arrange that a momentary switching signal, as distinct from a continuous one is provided in'response to the depression of a keyboard push-button since this simplifies the provision of a so-called multikey rollover facility.

According to the present invention therefore there is provided an electric switch of the push-button type affording a momentary switching action comprising a spring biased push-button which in response to the depression thereof causes a cam surface to bear against a springy moving contact member of the switch initially to produce bowing of the said contact member so that it makes electrical contact with or disengages from a fixed contact member and thereafter during the depression of the push-button to permit the compressive forces in the contact member to be released suddenly by snap deflection of the member as it rides over the cam surface thereby to interrupt or restore electrical contact with the fixed contact member by the straightening of the moving contact member.

The fixed contact member preferably comprises a coil spring which also serves as the biasing spring for the push-button in which case the springy moving contact member may be positioned at least partially inside the coil spring so that the moving contact member as it bows under the action of the cam makes contact with the inside of the coil spring.

By way of example the present invention will now be described with reference to the accompanying single FIGURE drawing which shows a diagrammatic crosssectional view of a key-switch according to the invention.

Referring to the drawing, the switch comprises an insulating body 1 which accommodates a coiled spring 2 biasing a push-button key 3 upwards as shown. This spring 2 also forms the fixed contact member of the switch. The moving contact member consists of a strip of springy metal 4 which is pre-bent into a serpentine shape. The fixed and moving contact members have 2 terminal parts 5 and 6 respectively, the base of the body 1.

For the operation of the switch the push-button key 3 is depressed against the action of the spring 2. The push-button has a concave cam surface 7 on its underside which bears down upon the turned over head of the springy strip 4 and by so doing the centre part of the strip 4 bows outwards until it engages with the inner surface of the spring 2. In this way closure of the switch contacts is effected but having made contact with the coil spring the force exerted on the strip 4 by continued downward movement of the push button 3 causes the head of the strip 4 suddenly to move up the cam surface 7 into the cavity 8 and in so doing the springy strip 4 restores substantially to its pre-bent shape as illustrated so that it disengages from the spring 2 and thereby breaks electrical contact therewith. It will therefore be appreciated that the switch affords a momentary make action.

After release of the push-button 3 the button is restored to the position illustrated and the head of the strip 4 accordingly moves out of the cavity 8 so that the top of strip 4 deflects to the right as viewed in the drawing and takes up the position illustrated.

From the foregoing it will be seen that the switch according to the invention is a very simple construction and although a switch having momentary make action has been described, a change-over or break switching action could alternatively be provided.

What we claim is:

1. An electric switch of the push-button type affording a momentary switching action during activation of the switch, the switch comprising a spring-biased pushbutton which in response to the depression thereof causes a cam surface to bear against a springy moving contact member of the switch initially to produce bowing of said contact member so that it makes electrical contact with or disengages from the inside of a coil spring constituting a fixed contact member and thereafter during the depression of the push-button to permit the compressive forces in the moving contact member to be released suddenly by snap deflection of the member as it rides over the cam surface thereby to interrupt or restore electrical contact with the fixed contact member by the straightening of the moving contact member.

extending through 

1. An electric switch of the push-button type affording a momentary switching action during activation of the switch, the switch comprising a spring-biased push-button which in response to the depression thereof causes a cam surface to bear against a springy moving contact member of the switch initially to produce bowing of said contact member so that it makes electrical contact with or disengages from the inside of a coil spring constituting a fixed contact member and thereafter during the depression of the push-button to permit the compressive forces in the moving contact member to be released suddenly by snap deflection of the member as it rides over the cam surface thereby to interrupt or restore electrical contact with the fixed contact member by the straightening of the moving contact member. 